The present invention relates to a weighing system for automatically and successively weighing articles up to a prescribed weight.
Weighing systems have a combinatorial weighing apparatus and a feeder for supplying articles to the combinatorial weighing apparatus.
The combinatorial weighing apparatus operates by distributing articles to a plurality of weighing machines arranged in a circular pattern, for example, around an article pooling or storage unit to enable the weighing machines to weigh the supplied articles, effecting a combinatorial weighing process based on the weights measured by the respective weighing machines to select an optimum added weight combination which is equal to or closest to a target weight within a prescribed error range, and discharging the articles from those weighing machines which give the optimum weight combination for thereby obtaining the articles with the total weight equal or closest to the target weight.
The article feeder is in the form of a bucket conveyor or a belt conveyor disposed closely to the combinatorial weighing apparatus for supplying the articles to the article storage unit. The article feeder does not continuously supply the articles to the article storage unit, but usually supplies the articles only when the quantity of articles pooled on the article storage unit is reduced below a predetermined level for preventing articles from being excessively supplied to the article storage unit. The weighing apparatus has a detector for detecting the amount of articles on the article storage unit. When the detector detects a prescribed reduction in the quantity of artices on the article storage unit, the article feeder is actuated to feed articles in the article storage unit. Heretore, the detector and the article feeder are coupled by an electric cord. This however has led to the following drawbacks:
The weighing apparatus and the article feeder are installed on a floor while they are interconnected by the electric cord. When the weighing apparatus and the article feeder or their surroundings are to be cleaned, the weighing apparatus or the article feeder is required to be individually moved. At this time, the electric cord becomes an obstacle to such movement of the weighing apparatus or the article feeder, or may be cut off by forcibly moving the weighing apparatus or the article feeder one from the other if the operator happens to foreget to disconnect the electric cord. Where food articles are weighed by the weighing system, the weighing apparatus and the article feeder will be washed with water for sanitary purpose after a desired sequence of weighing operation is over. When washing the weighing apparatus and the article feeder are washed with water, the connectors used for connecting the electric cord are covered with water and corroded, resulting in reduced electric conductivity.
The weighing apparatus includes a distributive or dispersive table surrounded by the weighing machines for supplying articles to the weighing machines. A plurality of vibratory supply troughs are disposed radially outwardly of the distributive table for supplying the articles which have been charged onto the table through the supply troughs into the corresponding weighing machines. Since the supply troughs have not been fixed to an attachment base, however, the efficiencies for cleaning the supply troughs and for inspecting and adjusting the vibrators have heretofore been poor. To solve this problem, the applicant has proposed a supply trough detachable from an attachment base as disclosed in Japanese Laid-Open Utility Model Publication No. 59-62516. The disclosed supply trough is mounted on a vibrator supported by a plurality of springs on a base plate. The supply trough and the vibrator are detachably attached to the attachment base by engaging a pin on the attachment base in an attachment hole defined in the base plate. With this disclosed arrangement, the supply trough can easily be detached from the attachment base as when the supply trough is to be washed, and hence can efficiently be washed.
In the disclosed supply trough, the springs interposed between the base plate and the vibrator comprises leaf springs which are however liable to be easily broken as they are not durable enough. If more durable coil springs were employed, then the following shortcomings would arise:
For connecting the coil spring ends to the upper surface of the base plate and the lower surface of the vibrator with a bolt, the bolt would be inserted through the coil spring. However, it would be extremely difficult to connect the coil spring ends to the upper surface of the base plate and the lower surface of the vibrator with the bolt. One solution to this problem would be to couple the upper end of the coil spring to the lower surface of the vibrator with the bolt, while keeping the lower end of the coil spring in engagement with the upper surface of the base plate with a pin or the like. With this fastening arrangement, however, the vibrator and the base plate would be separated from each other, and for attaching and detaching the supply trough to and from the attachment base, both of the base plate and the vibrator would have to be attached and detached. As a consequence, it would be highly troublesome to attach and detach the supply trough. If the coil spring ends were joined in some way to the upper surface of the base plate and the lower surface of the vibrator, then it would be difficult to disassemble the supply trough. It would also be difficult to adjust the height and inclination of the supply trough for smooth delivery of articles to be weighed therethrough or for avoiding interference with adjacent devices. More specifically, such height and inclination adjustment is normally effected by positioning a shim of a suitable thickness between the upper end of the spring and the lower surface of the vibrator or the lower end of the spring and the upper surface of the base plate. With the spring ends joined to the lower surface of the vibrator and the upper surface of the base plate, however, difficulty would be experienced in attaching and removing such a shim.
In case articles to be weighed are solid materials of fixed shape such as dried macaroni tubes or potate chips, they are prevented from being stagnant or attached as they slide along the distributive table and the supply troughs since the coefficient of friction of the articles are substantially constant. Accordingly, the weighing cycle and the opening and closing cycle of pool hoppers and weighing hoppers can remain substantially constant.
Where articles to be weighed are sticky materials such as pickled vegetables or syruped foods, or soft materials such as dried fruits or cheese, the articles are more likely to get stuck to the distributive table and the radial trough surfaces as they slide along. As a consequence, it takes a longer period time for these materials to slide along the distributive table and the supply troughs, and the articles are supplied randomly to the pool hoppers. Thus, the supply of the articles to the weighing hoppers downstream of the pool hoppers is also apt to become unstable, resulting in unstable weighing cycles. It is also difficult to control the timing of the supply of the articles from the supply troughs to the pool hoppers. Another problem with the sticky materials such as pickled vegetables or syruped foods is that the liquid also supplied with the articles along the distributive table and the supply troughs cannot be removed but is charged also into the pool hoppers and the weighing hoppers, resulting in different weights of packaged articles or goods.